Thermionic translating device



A. McL. NICOLSON. THERMIONIC TRANSLATING DEVICE.

APPLICATION FILED APR. 16. 1915.

I Patented June 24, 1919.

Mflfnesses:

' entwimng or "UNITED STATES PATENT OFFICE.

EXANDER McLEAN NICOLSON, or NEW YORK, 'N. Y.,, assrenon, BY mnsnnASSIGN- mnnrs, 'ro WESTERN ELECTRIC commmr, mcoarom'rnn, A conromrron onNEW YORK.

Specification of Letters Patent.

Application filed April 16, 1915. Serial No. 21,917.

To all whom it may concern:

Be it known that I, ALEXANDEKMCLEAN NIcoLsoN, a subject of the King ofGreat Britain, residing at New York, in the county of New York and Stateof New York, have invented certain new and useful Improvements inThermionic Translating Devices, of which the following is a full, clear,concise, and exact description.

This invention relates to thermionic translating devices andparticularly to a mechanical structure for supporting the cathodefilament of such devices. Its object is to insure a constant and uniformoutput of energy therefrom.

Trouble has been experienced in the past in connection with theemployment of filamentary cathodes in thermionic vacuum tube devices,due to the fact that the cathode filament when heated, becomes elongatedand unless some means is adopted for overcoming it, alateraldispla-cement or warping of the filament will occur. Inasmuch asthe energy output of a thermionic device of this sort is dependent,among other things, upon the distance between the cathode filament andthe other electrode members, it follows thatany warping of the filamenttoward or away from .the grid member for example, will cause analteration inthe constant-sol? the tube. It has, in the past,been-Tpr'o'posed where a filament of loop form has been used, to remedythis defect by providing a resilient support for the apex of the loopwhich places the filament under a certain amount of tension and takes upany expansion of the loop in such a way as to keep the loop insubstantially its initial plane. Such tension on the filament has beenfound, however, to be undesirable in certain instances, as tending todecrease the life of the filament.

In the present invention, an improved method of maintaining the filamentin its initial plane is provided which consists in threading thefilament on a supporting member so that it will be held by the saidsupport at a plurality of points distributed along its length. Whilethis arrangement does not, of course, prevent the linear expansion ofthe filament it minimizes the effect of such expansion in that itprevents the cumulative warpin effect and confines the warping to aplurality of relatively short sections, the result being that the totalefl'ectlve lateral displacement of the filament, due to the warping, iskept within reasonable bounds. The amount of this displacement can beregulated by the number of points at which the filament is directlysupported by the supporting member. By thus limiting the lateraldisplacement of the filament, the output of the tube-can be madeextremely constant.

The accompanying drawings illustrate some of the ways in which thefilament may be supported in accordance with this invention. Figure 1 ofthe drawings illustrates an audlon employing a cathode support of thetype inquestion; Fig. 2 shows in detail the way in which the filament issupported on the supporting member of Fig. 1; Figs. 3, 4, 5 and 6 showother arrangements of filament support which may be employed.

Referring in detail to Fig. 1 of the drawlngs, 7 is an evacuated glassvessel of the type customarily employed for audion bulbs. 8, ,8 are theanode or plate members of the audion electrode arrangement, 9, 9 are thegrid or input members and 10 is the filamentary cathode supported, inthis instance, on a frame 11 of mica. The way in which the filament 10is supported on frame 11 is illustrated in Fig. 2. Frame 11 has acentral opening 12 and a row of perforations or holes 13 is locatedoneither side of the central opening or window 12. The filament 10 whichis preferably made of a twisted platinum ribbon coated withthermionically active material is'threaded or laced through the holes 13in the manner shown. It will thus be seen that the filament is supportedPatented June-24, 1919.

in this particular instance at twelve difl'erent points in its lengthand it is therefore divided into eleven parts. As shown in the drawing aplurality of the electrodes are insulatingly supported by the unitarysupon the grid by means of glass or quartz beads 15 which are fusedaround the filament and the wire of the grid at their point of contact.It has been found that beads of this sort can be employed verysatisfactorily and that they can be applied without, in any way,injuring the active coating of the filament. The nickel oxid coating onthe wires of the frame 1-.L serves to insulate the filament. from the f'ame. I Where a metal supporting frame is used, as in the case of Fig.3, it has been found advisable to ground one end of the filament 10 tothe frame work 1 as at 16. This is for the purpose of preventing anyaccumulation of charge on the frame It and thus maintaining the filamentand its supporting frame work at the same potential. In the modificationillustrated in Fig. i, the supporting frameworr 17 is made ofquartz withnotches 18 cut in its outer edges, the filament 10 in this case beingzig-zaggcd in and out of the central opening 19 and supported by thewalls of the notches 18 as shown.

In the modification of Fi 5 an inverted U-shaped support 20 of oxidizednickel wire is used. The legs of this support are spiraled and thefilament is wound in and out between the two legs as shown. In a furthermodification of Fig. (3 the supporting member 21 is of glass. Thefilament is fastened by means of glass or quartz beads 15 to smalloxidized nickel wires which are fused into the legs of the support 21.All the modifications shown have the common property of supporting thefilament without tension at a plurality of points along its length insuch a manner that the lateral displacement due to linear expansion willnot be cumulative but, will be distributed among a plurality ofrelatively short sections, the terminals of which are rigidly held intheir initial plane. Furthermore, the lateral displacements of thevarious sections will not necessarily be in one direction as some of thesections will tend to warp in one direction and some in another. Thus itwill be seen that the effective active plane of the filament as a wholewill remain at a substantially constant distance from the otherelectrodes in thetube, thereby insuring constancy and uniformity in theoperation of the device as av whole.

'hat is claimed is:

1. A device of the audion type comprising a thermionic cathode, an anodeand an auxiliary elect-rode, means for supporting said auxiliaryelectrode, said cathode being filamentary in form, and a planarysupporting frame therefor parallel to one of. said electrodes andcomprising spaced parallel members.

2. In a thermionic translating device, members spaced apart comprising aplurality of filament supporting points, a filamentary cathode supportedthereon and vitreous bonds between said filament and its severalsupporting points.

3. In a thermionic translating device, a metal supporting frame, afilament supported ata. plurality of points by said frame, and aconductive connection between one end of said filament and said frame.

i. In a thermionic translating device, an input elect-rode, a supportingframe having a plurality of upright and transverse members and afilamentary cathode interwoven on said members and contacting therewithat a plurality of points whereby the effective plane of said cathode ismaintained at a substantially constant distance from said inputelectrode.

Parallel simporting members, a fila mentary thermionic cathodeinsulatingly supported at a plurality of points thereby, a grid frame ateach side of said cathode, and an arbor for supporting said members andsaid frames.

6. In a thermionic translating device, the combination of a plurality ofelectrodes, parallel members extending across the ends of saidelectrodes and insulatingly supporting said electrodes.

7. A thermionic device comprising an evacuated vessel, a press therefor,electrodes within said vessel, wires extending from a plurality of saidelectrodes, and an insulating member extending substantially parallel tosaid press and insulatingly supporting said wires.

8. A device of the audion type comprising an evacuated vessel, a press,parallel grids, a frame therebetween and a filamentary elec trode woundback and forth on said frame, substantially at right angles to the axisof said press.

9. A device of the audion type comprising an evacuated vessel, a. press,parallel grids, a frame adjacentthereto, and a filamentary cathode woundback and forth on said frame, substantially at right angles to the axisof said press.

10. A device of the audion type comprising parallel grids, a supporttherebet-wee'n comprising spaced parallel members, and a cathodeextending between said members and supported thereby.

11. A thermionic device comprising an evacuated vessel, a presstherefor, cathode and anode electrodes within said vessel, Wiresextending from said electrodes, and an insulating member extendingsubstantially parallel to said press and insulatingly supporting saidwires, said electrodes being arranged between said member and saidpress.

12. A thermionic device comprising an evacuated vessel, a presstherefor, cathode, anode and control electrodes within said vessel,Wires extending from said electrodes,

13. A thermionic device comprising an evacuated vessel, a presstherefor, cathode, anode and control electrodes, Wires extending fromsaid electrodes, and an insulating member extending substantiallyparallel to said press and insulatingly supporting said wires.

14. A thermionic device comprising an evacuated vessel, a press, asupport comprising parallel members and a connection therebetween and atrightangles' thereto, one of said members being fastened to said pressand extending substantially at right angles to the axis thereof,cathode, anode and control electrodes extending between said parallelmembers and supported thereby.

15. A thermionic device comprising an evacuated vessel, 3, press, asupport com- 'pr1s1ng parallel members and a connection therebetween andat right angles thereto, one of said members being fastened to saidpress and extending substantially at right angles to the axis thereof, acathode surface, two grid surfaces and two plate surfaces extendingbetween said parallel members and supported thereby.

16. A thermionic device comprising an evacuated vessel, a press, anarbor connected to said press, and a plurality of electrodes comprisinga pair of plate electrode surfaces, a pair of grid electrode surfaces,and a cathode supported by said arbor, said plate electrodes havingindividual supporting connections to said arbor.

In witness whereof, I hereunto subscribe my name this 14th day of April,A. D., 1915.

ALEXANDER MOLEAN NICOLSON.

